إشارة سيمافور السكك الحديد
أحد أقدم وسائل إشارة السكك الحديدية الثابتة هي السيمافور semaphore. These signals display their different indications to train drivers by changing the angle of inclination of a pivoted 'arm'. Semaphore signals were patented in the early 1840s by Joseph James Stevens, and soon became the most widely-used form of mechanical signal. Designs have altered over the intervening years, and colour light signals have replaced semaphore signals in some countries, but in others they remain in use.
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الأصول
أول سيمافور سكك حديدية أنشأه تشارلز هتن گريگوري في سكك حديد لندن وكرويدن (لاحقاً London Brighton and South Coast Railway) at New Cross, southeast London, about 1842 on the newly enlarged layout also accommodating the South Eastern Railway.[1] The semaphore was afterwards rapidly adopted as a fixed signal throughout Britain, superseding all other types in most uses by 1870. Such signals were widely adopted in the U.S. after 1908.
الربع الأسفل والربع الأعلى
Semaphores come in lower quadrant and upper quadrant forms. In a lower quadrant signal, the arm pivots downwards for the less restrictive (known as "off") indication. Upper quadrant signals, as the name implies, pivot the arm upward for "off".
الاستعمال
إشارات التوقف
الإشارات البعيدة
الإشارات المزدوجة للتوقف والبعد
انحسار الاستخدام
Mechanical signals worldwide are being phased out in favour of colour light signals or, in some cases, signalling systems that do not require lineside signals (e.g. RETB and the new European system ERTMS). In the United States, their usage has been almost completely eliminated on main lines, with significant remaining installations still found on two separate segments of the CSX Transportation line from Louisville, Kentucky to Chicago, Illinois, on the route of the former Monon Railroad.